Demilitarization of wax desensitized explosive projectiles

ABSTRACT

A method for demilitarizing projectiles, typically military projectiles, containing a class of energetic materials known as Composition A which are wax desensitized materials. The projectiles are opened to expose the wax desensitized energetic material, which is then removed from the projectile by fluid jet technology. The wax component is separated from the energetic particles only to a degree that will leave an effective amount of desensitizing coating of wax remaining on the particles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Provisional Application 61/278,511 filed on Oct. 7, 2009.

FIELD OF THE INVENTION

The present invention relates to a method for demilitarizing projectiles, typically military projectiles, containing a class of energetic materials known as Composition A which are wax desensitized materials. The projectiles are opened to expose the wax desensitized energetic material, which is then removed from the projectile by fluid jet technology. The wax component is separated from the energetic particles only to a degree that will leave an effective amount of desensitizing coating of wax remaining on the particles.

BACKGROUND OF THE INVENTION

Surplus projectiles present a unique problem to the US military. The US military must prioritize its spending to effectively defend the interests of the United States in this current period of tight budget constraints. Maintaining aging and surplus projectiles tightens defense budgets because it requires expenditures for security and storage facilities. Further, the US military must regularly destroy a significant amount of projectiles that are surplus, that have deteriorated, or that are obsolete.

In the past, projectile stocks have been disposed of by such methods as dumping them in the ocean, or by open burn/open detonation (OB/OD) methods. Although such methods effectively destroy projectiles, they fail to meet the challenge of minimizing waste by-products in a cost-effective manner. Further, such methods of disposal are undesirable from an environmental point of view because they contribute to contamination of the oceans and/or to the pollution of the atmosphere.

Projectiles containing wax as a desensitizing agent are presently in need of demilitarization. These projectiles are typically press-loaded projectiles containing a class of energetic material known as Composition A which is a highly brisant energetic formulation composed of cyclotrimethylenetrinitramine (RDX) and desensitizing wax. Composition A began to replace Explosive D (ammonium picrate) in the 1940s as the preferred energetic fill for U.S. Navy projectiles. The two most common Composition A formulations are Composition A-3 and Composition A-5. The variation in Composition A formulations arises from differences in the amount and composition of the desensitizing wax. In addition, some projectiles were filled with an aluminized version of Composition A in which powdered aluminum was added to the Composition A before press loading into a projectile. The Composition A projectile is fuzed in a variety of configurations in which each projectile can receive up to three fuzes—a base fuze threaded into the base of the projectile, a nose fuze threaded into the nose of the projectile, and an auxiliary detonating fuze located inside the projectile behind the nose fuze.

One of the most common formulations, Composition A-3, is prepared by adding melted wax, usually beeswax, and a surfactant to energetic crystals in hot water. The solution is mixed and passed through rollers and dried to form wax coated particles. The resulting composite particles were typically comprised of about 91 wt % energetic component and about 9 wt % wax. The particles are then press loaded into projectile casings (shells). The wax coating protects the energetic crystals from the intense point stresses and friction experienced during manufacturing, handling, and launch thus preventing premature detonation. A conventional method for demilitarizing wax desensitized projectiles was to use hot water to melt the wax with the expectation that the energetic crystals would settle out. Unfortunately, the degree of recovery of energetic fell substantially short of expectations. In addition, such technology cannot be used with aluminum containing projectiles, nor can it be applied to projectiles made with high melting point waxes (m.p. >100° C.). Another method involved the removal of the wax desensitized energetic material followed by dissolving the wax away from the energetic particles. Such a method could be problematic because it can lead to removing too much wax from the energetic particles, thus resulting in unstable sensitized energetic particles.

Thus, there is a need in the demilitarization art for processes that will meet the goals of resource reuse and recovery of the energetic component at commercially acceptable yields. The process of the present invention meets these goals with respect to the demilitarization of wax desensitized projectiles.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a process for demilitarizing a projectile containing a wax desensitized energetic material comprised of a wax component and an energetic particulate component, which process comprises:

a) exposing the wax desensitized energetic material in the projectile;

b) removing the wax desensitized energetic material from the projectile with the use of a fluid jet operated at a pressure from about 20,000 to about 150,000 psig thereby resulting in wax desensitized energetic particles having a fraction of the wax component separated therefrom, but leaving an effective amount of wax on said energetic material so that the energetic particles remain desensitized;

c) collecting the separated wax component; and

d) collecting the resulting wax desensitized energetic particles.

In a preferred embodiment the energetic component is selected from the group consisting of RDX and HMX.

In another preferred embodiment the projectile is a military shell and the fluid of the fluid jet is water.

In still another preferred embodiment of the present invention the pressure of the fluid jet is from about 40,000 psi to about 150,000 psi to wash out the wax sensitized energetic material.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 hereof is a plot of the wax content of the recovered wax coated energetic material after washout in accordance with the process of the present invention for experiments 1, 3, 8, 9, 10, 11, 12 and 13 hereof.

FIG. 2 hereof are plots of the cumulative mass fraction undersize versus size in microns for the recovered wax coated energetic material after washout for experiments 1, 2, 4, 5, 6, and 7 hereof.

FIG. 3 hereof are plots of the initial concentration and final concentration in ppm of RDX and HMX in the washout water for the experiments herein plus an additional 60 experiments.

DETAILED DESCRIPTION OF THE INVENTION

Projectiles that are the subject of this invention are wax desensitized projectiles. That is, projectiles that contain a major amount of energetic particles and a minor amount of wax to desensitize the energetic particles. The wax bonds and coats the energetic particle, thereby protecting them from the intense point stresses and friction experienced during manufacturing, handling, and launch. This prevents premature detonation. The wax can be any naturally occurring or synthetic wax that is suitable for use in projectiles. Waxes are typically referred to as “synthetic” if they are fractionally distilled from petroleum and in specific portions reblended. Natural waxes are waxes derived from animal, insect, mineral/petroleum, and vegetable sources. Non-limiting examples of waxes that are suitable for being recovered in the process of the present invention include: insect and animal waxes, preferably beeswax, Chinese insect wax, wool wax, and spermaceti; vegetable waxes, such as candelilla, carnauba, candelilla, Japan wax, ouricury wax, rice-bran wax, jocoba, castor wax, and bayberry wax; mineral waxes, such as montan wax, peat wax, ozokerite and ceresin waxes; petroleum waxes, such as paraffin and microcrystalline waxes; and synthetic waxes, such as polyethylene waxes, and mixtures thereof. The most preferred wax is beeswax since there is a substantial stockpile of projectiles that contain beeswax as a desensitizing agent.

In order to demilitarize projectiles containing wax desensitized energetic particles, under modern demilitarization requirements, all components of the projectiles need to be recovered. Prior art attempts to recover the wax component from the energetic component involved the use of hot water to melt the wax with the expectation that the energetic component would merely settle out. Surfactants were some times added to improve the separation of the explosive from the water/wax phase, but the degree of separation was far less than desirable and not commercially feasible. The present invention is capable of overcoming these shortcomings.

Non-limiting examples of energetics that can be used in wax desensitized projectiles include: cyclotrimethylenetrinitramine (RDX); cyclotetromethylene tetranitramine (HMX); 2-methyl-1,3,5-trinitrobenzene (TNT); Amatol (Ammonium Nitrate/TNT); Cyclotol (RDX/TNT); Octol (HMX/TNT); and any of the preceeding combined with aluminum particles (Al). Preferred are RDX, TNT, and HMX.

Non-limiting examples of standard military energetics containing waxes are: Composition B and B-5 (RDX/TNT); Torpex 2 and Torpex D-1 (RDX/TNT/Al); HBX, HBX-1, and HNX-3 (RDX/TNT/Al); H-6 (RDX/TNT/Al); Composition A-3, A-5, A-6, A-7 (RDX).

In order to demilitarize the projectile containing the Composition A material, the projectile casing must be opened to expose the energetic material. Typically, projectiles containing Composition A material have a threaded fuze at their base or nose which can be safely removed, such as by specialized equipment. In the event that a fuze component cannot be safely removed, by unthreading, any suitable technique can be used to expose the energetic material. For example, the energetic material can be exposed by cutting open the shell using any appropriate cutting method known in the art. One preferred cutting method is the use of an abrasive fluid jet. One method is to cut projectile casing across its longitudinal axis at a point that would expose substantially all of the wax desensitized energetic for removal. That is, the fuze end of the casing. The wax desensitized energetic material can also be exposed by removing the fuse, or fill plug, of the casing, thereby exposing the wax desensitized material.

Another method, which is preferred, is to simultaneously remove the fuze from a plurality of projectiles by use of a plurality of fluid jets. A material handling system moves live projectiles through the demilitarization process. Such a system is preferably comprised of a conveyor system such that one end is located in an area where live projectiles can be loaded onto the conveyor. The conveyor has carriers fitted onto it such that each carrier can hold a plurality, preferably a maximum of 4 projectiles. The carriers are also fitted with 4 inserts specifically sized to hold a given type of projectile. The projectile is placed in the insert on the carrier in one of the two vertical positions. If the base fuse is manually unthreaded from the projectile or requires cutting, it will be loaded with the nose up so that the high-pressure fluid jet can cut or wash out the projectile. If the nose fuze is manually unthreaded from the projectile, it will be loaded in the nose down position. Orientation of the projectile requires the end placed upward to be closed so that washout can be accomplished without material issuing from the top of the projectile.

The projectiles can be moved to fuze cut-out stage. The projectiles are positioned so that the surface of each projectile containing a fuze opposes a fluid jet nozzle that is positioned to direct a jet of high-pressure fluid in a predetermined path around the perimeter of the fuze. It is preferred that the path be a closed path since the fuze will typically have a circular shape. The projectiles can be made to rotate so that the jet of fluid from the nozzles are directed in the predetermined path around the outside perimeter of the fuze. Alternatively, the nozzles can be made to rotate to track the same predetermined path around the perimeter of the fuze. It is within the scope of the present invention that both the projectiles and the nozzles rotate. It is preferred that the projectiles be rotated and that the fluid jet apparatus, such as a wand containing the nozzle, be substantially rotationally static and moves only longitudinally to the body of the projectile. The fluid jet will be of sufficient pressure to cause cutting of the projectile casing. The cutting of the projectile casings to remove the fuzes may be done by either of two procedures. For example, in one procedure the cutting can be conducted gradually along the cutting path around the perimeter of the fuze by making multiple passes along the cutting path until the fluid jet cuts through the casing and the fuze is isolated and washed free of the casing by the cutting fluid. During this procedure, the depth of the cut during each pass along the cutting path increases gradually so that piercing, or cutting entirely through, the casing is a gradual process. This procedure is preferred when it is only desired to remove the fuze and not to immediately remove the energetic material from the projectile. Alternatively, in another procedure, the pressure of the fluid jet can be substantially increased so that the base of the projectile is pierced and the high pressure fluid jet is directed along the cutting path only once while cutting entirely though the base of the casing during its travel around the perimeter of the fuze. This procedure has the advantage of removing the fuze of the projectiles while simultaneously removing at least a portion of the energetic material. The operating pressure of the fluid jets will be from about 20,000 to about 150,000 psig, preferably from about 40,000 to about 150,000 psig.

The fluid will preferably contain an abrasive material to enhance cutting. Non-limiting examples of abrasive materials that are suitable for use in the present invention include glass, silica, alumina, silicon carbide, garnet, as well as elemental metal and metal alloy slags and grits. The preferred abrasive material is garnet. It is preferred that the abrasive either have sharp edges or that it be capable of fracturing into pieces having sharp cutting edges, such as for example, octahedron or dodecahedron shaped particles. The size of the abrasive particles may be any suitable effective size. By effective size, is meant a size that will be effective for cutting the metal shell casing (typically a metal alloy, such as steel) and which is effective for forming a substantially homogeneous mixture with the fluid carrier. Useful particle sizes of abrasive material range from about 3 mm to 55 microns, preferably from about 15 mm to 105 microns, and most preferably from about 125 microns to about 250 microns. Generally, the most preferred abrasives have been found to be garnets and aluminum-based materials having a particle size from about 125 microns mesh to about 250 microns.

The concentration of the abrasive within the fluid will range in slurry fluid jet systems from about 1 to about 50 wt. %, preferably from about 10 to 40 wt. %, and most preferably from about 25 to 35 wt. %. For entrained fluid jet systems, the amount of abrasive will generally comprise about 5 wt. % to 30 wt. %, preferably from about 10 wt. % to about 25 wt. % of total fluid plus abrasive, depending on the diameter of the orifice of the nozzle. Increasing the concentration of an abrasive, generally, has a tendency to increase the cutting efficacy of the fluid jet.

The fluid of the fluid jet can be any suitable composition that is normally a liquid. By “normally liquid” we mean that it will be in the liquid state at substantially atmospheric temperatures and pressures. For example, it can be water or an organic solvent, in which at least a portion of the energetic or wax component is at least partially soluble. In one preferred embodiment of the present invention, the fluid used to cut out the fuze(s) is water, plus an abrasive, and the fluid used to washout, or cut out, the energetic material from the projectile is also water. It is preferred that the fluid be nontoxic so as to maintain the environmental usefulness of the cutting/demilitarization process. Non-limiting examples of organic solvents suitable for use in the practice of the present invention include: alkyl alcohols, alkyl ketones, alkyl nitriles, nitroalkanes, and halo-alkanes. More particularly, the alkyl group of the organic solvent may be branched, cyclic, or straight chain of from about 3 to 20 carbons. Examples of such alkyl groups include octyl, dodecyl, propyl, pentyl, hexyl, cyclohexyl, and the like. Methanol and ethanol are the preferred alcohols. The alcohols may also contain such alkyl groups. Non-limiting examples of ketones include acetone, cyclohexanone, propanone, and the like. Non-limiting examples of nitro compounds that can used as the carrier for the fluid jet in the practice of the present invention are acetonitrile, propylnitrile, octylnitrile, and the like. Non-limiting examples of halogenated alkanes include methylene chloride, chloroform, tetrahaloethylene and perhaloethane, and the like. Preferably, aqueous and aqueous/organic mixtures are used as the fluid which are more preferably nontoxic and cost effective, given the compatibility with the explosive material to be removed. Such more preferred fluids include, propylene and ethylene glycol, fuel oil compositions such as gasoline and diesel oil, water, short chain alkyl alcohols, mineral oil, glycerine, and mixtures thereof. Water is the most preferred.

The wax desensitized energetic material can also be removed from the projectile by use of fluid jet washout technology at pressures that are effective to erode, or comminute, the wax desensitized energetic material. The preferred type of fluid jet washout equipment which can be used in the practice of the present invention is described in U.S. Pat. No. 5,737,709 which is incorporated herein by reference. It is preferred that the fluid jet washout step of the present invention be able to achieve a 5× cleanliness that is required by Army Material Command Regulation 385-5 for energetics and Army Material Command Regulation 385-61 for chemical weapons. The operating pressure of the fluid jets will be from about 20,000 to 150,000 psi, preferably from about 40,000 to 150,000 psi. The preferred range of pressures can be used provided that the diameter of the washout stream is in the range of about 0.001 inch to about 0.02 inch.

There are a variety of Composition A formulations. The earliest type was comprised of RDX and beeswax. Later formulations replaced beeswax with synthetic waxes along with the addition of additives such as surfactants. It is preferred to prevent the formation of emulsions in which the non-RDX portion of the formulation blends with the fluid to form an emulsion. Although formation of emulsions may not be necessarily bad, avoiding their formation is beneficial. The addition of a surface-tension modifying material, such as an alcohol, to the high-pressure washout fluid can mitigate emulsion formation during washout.

If emulsions form in the process of washing out a projectile, they can be handled by carefully controlling the temperature of the emulsion. During the washout process, the maximum temperature that can be generated is dictated thermodynamically and termed stagnation temperature in which a fluid jet impinges on a surface, decelerates, and converts PV work into heat. The temperature rise for an 800 m/s waterjet is approximately 75° C. As a result, the washout fluid and removed energetic material will be heated as it is removed from the projectile. The careful monitoring of the washout material temperature and subsequent handling/cooling is critical.

If base fuzes are removed via high-pressure abrasive fluid jet cutting, the collected spent abrasive, swarf, and water is preferably separated as described in U.S. Pat. No. 7,225,716, which is incorporated herein by reference. Since the RDX component of Composition A is substantially insoluble in water (˜100 ppm at room temperature), the recovered water can be recycled to the high pressure pump provided substantially all insolubles are removed. This is acceptable even though the water may be saturated with RDX because the increase in pressure in the pump increases the solubility of RDX i.e. RDX will not precipitate.

It is within the scope of the present invention that the washout fluid be chilled to a temperature below the melting point of the wax component of the wax desensitized energetic material. If chilled, it is preferred that it be at a temperature from about 40 to 60° F., more preferably to a temperature from about 50 to 60° F.

It is important to note that the energetic material is removed from the projectile as a solid that is fractured from the energetic fill. It is preferred to remove the material from the projectile by leaving the RDX/wax coating intact thus minimizing the amount of wax liberated from the RDX and hence minimize the chances of emulsion formation. Nonetheless, the washed out material along with the fluid (water or water with an additive) must be collected and separated. It is desired to dewet the solid material so that it can be packaged for use in commercial energetic markets. The washed out material will be collected in a sump and educted to the downstream separation equipment. Heat transfer equipment can be integrated into the collection equipment to quickly cool the washed out material.

Once the washed out material is moved from the washout process, a variety of equipment types can be used to dewet, or dry, the solid material. This equipment may include clarifier/augers, screen filters, and dryers if the moisture content is critical for commercial uses. This separation process will most likely be continuous. The water can be recycled back to the high pressure pump, preferably without the need for further treatment. However, if the levels of energetic component must be reduced, or if the wax content/additive content is too high, additional equipment such as adsorption units or particulate filters can be used. One processing option that may be required is the addition of wax to the washed out wax desensitized energetic material. This will be required if it is determined that too much of the wax was removed from the energetic particles during the washout to meet commercial market specifications and desired shipping classifications.

Empty projectiles can be inspected as they are removed from the conveyor. This operation has traditionally been done via 100% human inspection. An automated vision system with cameras and machine vision technology can replace the human inspection process. In addition, robots could be used to load and unload projectiles into the system eliminating the need for human interface for these operations also. All of the camera/machine vision can be integrated into the logic control system. This integration would lead to more efficient operations and improve safety since humans are removed from operations involving the handling and verification of energetic materials.

If the fluid used for the fluid jet is water, the washed out wax desensitized energetic material, which is now in particulate form, is dried by conventional drying. It is within the scope of this invention that the dried resulting wax energetic material be treated with a solvent to remove at least an additional portion of the wax. It is also within the scope of this invention to combine the steps of removal of the wax desensitized energetic material and solubilizing the wax. For example, a fluid jet can be used to remove the material from the shell, and the fluid can be a solvent with respect to the wax.

The present is better illustrated by the following examples that are not to be taken as limiting in any way.

EXAMPLES

Each of 13 experiments was conducted by washing out a US Navy 5″projectile that was loaded with Composition A-3. Each experiment consisted of placing the projectile nose down in a station fitted with a high-pressure washout nozzle that could be raised and lowered into and out of the projectile. The projectile was placed nose down since the nose fuze was previously removed and hence acted as an entry point for the high-pressure washout nozzle. Next, the projectile was rotated at 20 rpm and the high-pressure water flow through the washout nozzle was turned on. After turning on the water, the washout nozzle was raised at a constant rate to within a few inches of the base of the projectile and then retracted all the way down. The washout water and energetic fill removed from the projectile was collected and separated. A sample of the energetic fill was dried and a 200 gram portion of the dried sample was sifted using a set of U.S. Sieves per MIL-C-440C and a 1 gram sample was analyzed to determine the wax content gravimetrically by dissolving the wax in naphtha and weighing the remaining RDX/HMX per MIL-C-440C. The washout water separated from the energetic fill was lastly processed through an activated carbon bed to remove the solubilized RDX and HMX.

For each of the 13 experiments, there were four important parameters that could be varied. These were the water pressure, water flow rate, the washout nozzle lift rate into the projectile, and the washout wand retract rate out of the projectile. The following Table 1, summarizes these values for each experiment.

TABLE 1 Water Water Washout Nozzle Washout Nozzle Pressure Flow Lift Rate Lift Retract Experiment (psi) (gpm) (inches/min) (inches/min) 1 52,000 0.96 1 3 2 52,000 0.96 2 3 3 40,000 1.69 2 3 4 42,000 0.86 1 3 5 42,000 0.86 2 3 6 42,000 0.86 1 3 7 42,000 0.86 2 4 8 35,000 0.39 1 3 9 55,000 0.99 3.5 3.5 10 55,000 0.49 2 3 11 55,000 0.49 4 4 12 56,000 0.50 2 1 13 54,000 0.49 2.5 2.5

The data obtained from these experiments are presented in the plots of FIGS. 1 to 3 hereof. The plots of FIG. 1 hereof show the wax content of the recovered energetic material from 8 different Composition A-3 filled projectiles that were washed out with high-pressure water. The plot shows that all of the recovered energetic, after washout, still had a wax content within the 8-10% range that the original material had when it was loaded into the projectiles, per mil-spec MIL-C-440C. Mil-spec refers to United States Military Standards or Specifications. In other words, the recovered material still meets the wax content specification that the virgin material had to meet when it was originally loaded and conforms we are not removing a significant amount of wax during the washout process.

The plots of FIG. 2 hereof show the particle size distribution of Composition A-3 from 6 different projectiles after being washed out with high-pressure water. These plots shows that a narrow particle size distribution is generated ranging from 200 to 400 microns. This particle size distribution also meets the original mil-spec MIL-C-440C which states that 100% of the material needs to pass through U.S. Sieve #6 (3350 microns) and a maximum of 5% can pass through U.S. Sieve #100 (152 microns).

The plots of FIG. 3 hereof show the treatment of the washout water that is contaminated with RDX and HMX. The washout water was from these 13 experiments plus an additional 60 experiments, thereby providing a higher concentration of RDX and HMX in the washout water. The initial concentration of the RDX in the water ranges between 40 and 85 ppm which depends upon temperature and agrees with the solubility in water. The initial concentration of HMX ranges from 5 to 10 ppm which also depends upon temperature and agrees with the solubility in water. The final concentration of both species in the water as it leaves a carbon adsorption bed is zero until about 700 gallons of water was treated. At this point the RDX and HMX broke through the bed and rose as the carbon bed became saturated. This profile is common for carbon adsorption systems and shows that carbon can be used to treat the washout water. 

1. A process for demilitarizing a projectile containing a wax desensitized energetic material comprised of a wax component and an energetic particulate component, which process comprises: a) exposing the wax desensitized energetic material in the projectile; b) removing the wax desensitized energetic material from the projectile with the use of a fluid jet operated at a pressure from about 20,000 to about 150,000 psig thereby resulting in wax desensitized energetic particles having a fraction of the wax component separated therefrom, but leaving an effective amount of wax on said energetic material so that the energetic particles remain desensitized; c) collecting the separated wax component; and d) collecting the resulting wax desensitized energetic particles.
 2. The process of claim 1 wherein the fluid of the fluid jet is water.
 3. The process of claim 1 wherein the pressure of the fluid jet is from about 40,000 psig to about 150,000 psig.
 4. The process of claim 1 wherein the wax is a naturally occurring wax.
 5. The process of claim 4 wherein the wax is a beeswax.
 6. The process of claim 1 wherein the wax is a synthetic wax.
 7. The process of claim 1 wherein the energetic component is selected from the group consisting of cyclotrimethylenetrinitramine (RDX); cyclotetromethylene tetranitramine (HMX); 2-methyl-1,3,5-trinitrobenzene (TNT); Amatol (Ammonium Nitrate/TNT); Cyclotol (RDX/TNT); and Octol (HMX/TNT).
 8. The process of claim 1 wherein there is also present aluminum particles along with the energetic particles.
 9. The process of claim 7 wherein the energetic is selected from the group consisting of RDX, TNT, and HMX.
 10. The process of claim 1 wherein the wax desensitized material is exposed by cutting open the projectile by use of a high pressure fluid jet.
 11. The process of claim 10 wherein the fluid of the fluid jet is water and wherein there is also present an abrasive material.
 12. The process of claim 11 wherein the abrasive material is selected from the group consisting of glass, silica, alumina, silicon carbide, garnet, as well as elemental metal and metal alloy slags and grits.
 13. The process of claim 12 wherein the abrasive material is garnet. 